The present invention relates to a facsimile apparatus having an error correction mode, and especially to a facsimile apparatus which can reduce the time necessary for the procedure between pages and the subsequent procedure (a procedure subsequent to the last page image information transmission procedure) for communication.
In prior facsimile apparatuses, generally, image information is transmitted at a high speed of, for example, 14.4 Kbps or the like, and other control signals are transmitted at a low speed of about 300 bps. In FIGS. 11 to 15, transmission procedures in an error correction mode of a facsimile apparatus having the error correction mode are shown. As is widely known, the error correction mode is a mode in which image information, having errors caused by noises, is sent again to a receiving side at its request, so that the receiving side can correctly receive the image information.
FIG. 11 shows a single page image information transmission procedure in which: when a transmission side dials and a communication line is connected with a receiving side, a CED signal (a called station identification signal) is sent from the receiving side to the transmission side at 300 bps; and next, an NSF signal (a nonstandard device signal), a CSI signal (a called station identification signal), and a DSI signal (a digital identification signal) are sent to the transmission side. Next, a TSI signal (a transmission station identification signal), and a DCS signal (a digital command signal) are sent from the transmission side to the receiving side.
When the preceding procedure (a procedure preceding the first page image information transmission procedure) has been completed as described above, a training signal T is sent from the transmission side at high speed, and a transmission speed of the image information is determined thereby. After that, the image information is divided into n frames, and the frames, from frame 1 to frame n, are successively sent to the receiving side. When the image information has been sent out, an RCP signal (a Return to Control for Partial Page signal) is sequentially sent out three times.
Next, a preamble Pr and a PPS-EOP signal (a Partial Page Signal-End Of Page signal, an EOP signal being a procedure completion signal) are sent out. This signal includes information by which the number of transmitted frames of image information is shown. Next, the preamble Pr and an MCF signal (a message confirmation signal) are sent out from the receiving side.
After the transmission side has received the above signals, the transmission side sends the preamble Pr and a DCN signal (a disconnection command signal), and thereby the communication line is disconnected and the communication is completed. In these communication procedures, a procedure subsequent to the RCP signal takes a relatively long period of time, 3.805 s, in the example. This is because each control signal is transmitted at the low speed of 300 bps so that communication can be surely performed.
FIG. 12 shows a multi-page transmission procedure, which is a communication procedure when a mode, such as resolution or density, is not changed. In the explanation of the example, the preceding procedure will be neglected hereinafter. In the drawing, after the transmission side has sent out the n-th page image information subsequent to the training signal, the RCP signals are successively sent out three times. Next, the transmission side sends out the preamble Pr and a PPS-MPS signal (a PPS-Multi Page Signal, an MPS signal being a multi-page signal). The PPS-MPS signal shows that image information of the n-th page has been transmitted and the control returns to phase C.
After receiving the above signals, the receiving side sends out the preamble and the MCF signal. Subsequently, the transmission side sends the training signal T, and next, sends the image information of the (n+1)th page. After the information of all pages has been sent out, the subsequent procedure is carried out in the same way as shown in FIG. 11, and communication is completed. In this case, the procedure between pages is also carried out at the transmission speed of 300 bps, and it takes 1.745 s.
FIG. 13 shows a transmission procedure when a mode is changed in the multi-page transmission. In this case, the transmission side sends a PPS-EOM signal (an EOM signal: an end of message signal) at the transmission speed of 300 bps in the procedure between pages. After the receiving side has sent the MCF signal, a waiting time of 6 s is provided for a modal change in the receiving side, and after that, the receiving side sends the NSF signal, CSI signal, and DIS signal in the same way as the foregoing.
After receiving the above signals, the transmission side sends the TSI signal and DCS signal. Next, the training signal T is sent out and the transmission speed is determined. After that, the image information of the (n+1)th page is sent out. After the image information of all pages has been sent out, the same procedure as shown in FIG. 11 is carried out and the communication is completed. In this case, the procedure between pages takes 8.57 s.
FIG. 14 shows a transmission procedure when an error frame is generated. In this case, the transmission side sends the preamble Pr and a PPS-XXX signal (XXX means any of EOP, MPS or EOM) in the procedure between pages, and next, the receiving side sends the preamble Pr and a PPR signal (a Partial Page Request signal). Information of a frame number in which an error has occurred, for example, a frame number 5 or 8, is included in the PPR signal.
After receiving the error frame information, the transmission side sends again the frame in which an error has occurred. Thereby, image information containing no error can be sent and received. In this case, the procedure between pages takes 3.485 s. The subsequent procedures are performed in the same way as shown in FIG. 11.
FIG. 15 shows a transmission procedure in the case where an error frame has been generated and a fall back is performed, that is, in the case where a transmission speed is lowered when the error has occurred. In the drawing, in the case where an error has occurred when the n-th page image information has been sent, for example, at the transmission speed of 14.4 Kbps, the PPS-XXX signal is sent in the same way as shown in FIG. 14 from the transmission side, and next, the PPR signal is sent from the receiving side.
Subsequent to the foregoing, the transmission side sends the preamble Pr and a CTC signal (a Continue To Correct signal). In the CTC signal, information of the transmission speed of the next image information is included. In this case, a transmission speed lower than the preceding transmission speed of 14.4 Kbps, for example, 9.6 Kbps is set. After receiving the signal, the receiving side sends the preamble Pr and a CTR (Response for Continue to Correct) signal. The CTR signal means that the CTC signal has been received.
Due to the foregoing, the procedure between pages is performed in the time of 6.005 s. After that, information of a frame in which an error has occurred is sent again at the transmission speed of 9.6 Kbps. Thus, when an error occurs, the transmission speed is lowered one step by one step, and communication is performed. The subsequent procedure is performed in the same way as shown in FIG. 11.
As described above, in the prior facsimile apparatus having an error correction mode, the image information and the RCP signal are sent out at the high transmission speed of 14.4 Kbps the maximum, and other control signals except the RCP signal are sent at a low transmission speed of 300 bps, so that the procedure between pages and the subsequent procedure take a relatively long time. Especially, when it is necessary to send information of a lot of pages, it takes a long time to transmit the information, so that the communication costs are increased.